Currently, a dental implant is a “root” device used in dentistry to support restorations that resemble a tooth or group of teeth to replace missing teeth. The dental implants, abutments, and dental prostheses are collectively called dental restorations or implant systems that resemble a tooth or group of teeth (referred to as “restoration” or “implant system”) as replacements for missing teeth. A dental implant generally appears similar to an actual tooth root and is placed within the bone of the jaw to replace the root of the missing tooth. After the implant surface fuses with the surrounding jaw bone (osseointegration), dental abutments and other dental prostheses, such as crowns, implant-supported bridges or dentures, can be installed. The dental abutments and prostheses then allow a patient to use the restorations for chewing (also called masticatory loading).
The process of placing the dental implants into the jaw bone of a patient is called dental implantation, and it is a very vigorous surgical procedure, resulting in bone damage at the bone-implant interface. A relatively long healing period follows this dental implantation process, which lasts at least about two to three months and may extend to six months. During the healing period, (1) the bone damage is repaired and replaced with new bone tissues (active biological bone remodeling); and (2) direct bone ingrowth or fusion between the implant surface and the bone tissue surrounding the implant is also achieved (osseointegration). If the healing time is too short before any masticatory force is applied on the implant, the implant might risk failure because of the bone damage in the pre-existing interfacial bone, weak new bone tissues, and unstable bone-implant interface with partial osseointegration. The masticatory force applied on an insufficiently healed implant creates excessive micro-motion between bone and implant surface, resulting in fibrous tissue development at the interface which might block further osseointegration and cause eventual failure of the implant system.
To prevent or reduce any possible direct masticatory force being applied on the implant, the installed implant is protected under a healing cap during the healing period. After a sufficient healing period, a second surgery is conducted to install an abutment and prosthesis (artificial tooth crown). The combination of these two surgeries results in an implant system that is regarded as a dental replacement for the missing tooth.
Most patients who need dental implantation have various levels of bone deficiency due to oral bone complications that cause the initial extraction of teeth and bone loss following extraction. For example, tooth extraction and disuse atrophy arising from delayed treatment can lead to loss of the alveolar ridge. Segmental oral reconstruction surgeries are likely to result in substantial defects and disconnections in the mandibular bone. A posterior maxillary tooth extraction occasionally produces too thin sinus floor. Often, bone augmentation is required to place implants in oral bone sites with too severe a bone defect.
Bone grafting surgery is a popular method to treat the bone deficiency in many critical oral defects. Autologous bone has been accepted as an ideal material for grafting allogeneic grafts, which is obtained from human cadavers and animals. However, these bone materials bring the risks of infection and immune rejection. In addition, the degree of bone incorporation or growth through the bone grafting process is uncertain and unclear. Further, many clinical cases reported post-implantation failures at the bone grafted sites after the bone grafting process. In addition, the grafting for bone augmentations imposes additional surgical steps for patients, increasing the overall treatment costs.
Many studies indicated that growth factors can be introduced to induce bone augmentation, and it has been suggested that bone morphogenetic protein (BMP) has the most potent ability for stimulating bone growth. However, a high BMP dose was shown to cause uncontrolled progress of bone augmentation next to the implant. Substantial marginal bone loss adjacent to implants can arise from oral bone disease, including osteoporosis and peri-implantitis under high impact loading of static occlusion and dynamic mastication. Revision surgeries are often required to treat these post-implantation complications. Thus, development of a new implantation strategy that can minimize the additional pre- and post-implantation surgeries is needed.